Southern GEMS groups II: HI distribution, mass functions and HI deficient galaxies

We investigate the neutral hydrogen (H i) content of 16 groups for which we have multiwavelength data including X-ray observations. Wide-field imaging of the groups was obtained with the 20-cm multibeam system on the 64-m Parkes telescope. We have detected 10 previously uncatalogued H i sources, one of which has no visible optical counterpart. We examine the H i properties of the groups, compared to their X-ray characteristics, finding that those groups with a higher X-ray temperature and luminosity contain less H i per galaxy. The H i content of a group depends on its morphological make-up, with those groups dominated by early-type galaxies containing the least total H i. We determined the expected H i for the spiral galaxies in the groups, and found that a number of the galaxies were H i deficient. The H i deficient spirals were found both in groups with and without a hot intragroup medium. The H i deficient galaxies were not necessarily found at the centre of the groups, however, we did find that two-thirds of H i deficient galaxies were found within about 1 Mpc from the group centre, indicating that the group environment is affecting the gas loss from these galaxies. We determined the H i mass function for a composite sample of 15 groups, and found that it is significantly flatter than the field H i mass function. We also find a lack of high H i mass galaxies in groups. One possible cause of this effect is the tidal stripping of H i gas from spiral galaxies as they are pre-processed in groups.